Maternofetal outcomes in early-onset gestational diabetes: does weight gain matter?

AIM: Women with early-onset gestational diabetes mellitus (GDM) have overall lower gestational weight gain (GWG) compared to those with later-onset GDM, albeit with usually worse maternofetal outcomes. We intent to investigate the association between inadequate GWG and maternofetal outcomes in pregnant women with early-onset GDM. METHODS: We performed a retrospective study of women with early-onset GDM based on the National Registry of GDM. Three study groups were defined according to the recommendations of the Institute of Medicine for GWG: excessive GWG (eGWG), adequate (aGWG) or insufficient (iGWG). RESULTS: A total of 8040 pregnant women were included: 27% (n = 2170) eGWG, 31% (n = 2492) aGWG and 42% (n = 3378) iGWG. Preeclampsia (4.3 vs 3 vs 1.6%, p < 0.001), polyhydramnios (3.1 vs 2.3 vs 1.8%, p = 0.008) and cesarean section (37.4 vs 34.1 vs 29.5%, p < 0.001) were significantly more frequent among women with eGWG. Additionally, there was a higher frequency of macrosomia (8.1 vs 3.6 vs 2.4%, p < 0.001), large-for-gestational-age (8.2 vs 3.7 vs 2.6%, p < 0.001) and birth trauma (2.6 vs 1.5 vs 1.1%, p < 0.001) in this group. On the other hand, fetal death (0.2 vs 0.2 vs 0.5%, p = 0.04), small-for-gestational-age (9 vs 10.3 vs 14.9, p < 0.001) and preterm delivery (5.6 vs 7.1 vs 7.5%, p = 0.03) were more frequent in iGWG group. CONCLUSIONS: Over two-thirds of pregnant women with early-onset GDM had inappropriate GWG, which was significantly associated with adverse maternofetal outcomes. Weight management must be a focus of special attention in women with early-onset GDM, beyond glycemic control, to achieve healthy pregnancy outcomes.

Mild periconceptional hyperglycemia: predictor of adverse fetomaternal outcomes in gestational diabetes?

AIM: To clarify whether mild first trimester hyperglycaemia (characteristic of early-onset GDM) is associated with higher incidence of congenital malformations and other adverse fetomaternal outcomes compared to women with second trimester hyperglycaemia (later-onset GDM). DESIGN AND METHODS: We analyzed the Portuguese National GDM database, containing data collected between 2011 and 2017. Two study groups were defined: Group 1-Women with GDM diagnosed during the first trimester (with fasting glycemia ≥ 92 and < 126 mg/dL); Group 2-Women with GDM diagnosed after the first 12 weeks of gestation, with either fasting glycemia or oral glucose tolerance test, according to the International Association of Pregnancy and Diabetes Study Group criteria. The fetomaternal characteristics of each group were compared. RESULTS: A total of 18.518 pregnant women diagnosed with GDM were included which 34.4% of them belonged to Group 1. Pregnant women from this group were significantly younger and had a higher median BMI than the women from the other group. Overall, there was no significant differences in maternal morbidity parameters between groups. Non-evolutive pregnancies were significantly more frequent along the present gestation in the group 1 (1.1% vs. 0.1%, p < 0.001), as was fetal death (0.6% vs. 0.2%, p < 0.001). Congenital malformations did not differ significantly between groups (3.2% vs. 2.8%, p = 0.155). CONCLUSIONS: The mild near conceptional hyperglycaemic state characteristic of an early-onset GDM seems to be associated with an increased prevalence of non-evolutive pregnancies and foetal deaths when compared to later-onset GDM.

MicroNiche: an R package for assessing microbial niche breadth and overlap from amplicon sequencing data.

Niche is a fundamental concept in ecology. It integrates the sum of biotic and abiotic environmental requirements that determines a taxon's distribution. Microbiologists currently lack quantitative approaches to address niche-related hypotheses. We tested four approaches for the quantification of niche breadth and overlap of taxa in amplicon sequencing datasets, with the goal of determining generalists, specialists and environmental-dependent distributions of community members. We applied these indices to in silico training datasets first, and then to real human gut and desert biological soil crust (biocrust) case studies, assessing the agreement of the indices with previous findings. Implementation of each approach successfully identified a priori conditions within in silico training data, and we found that by including a limit of quantification based on species rank, one could identify taxa falsely classified as specialists because of their low, sparse counts. Analysis of the human gut study offered quantitative support for Bacilli, Gammaproteobacteria and Fusobacteria specialists enriched after bariatric surgery. We could quantitatively characterise differential niche distributions of cyanobacterial taxa with respect to precipitation gradients in biocrusts. We conclude that these approaches, made publicly available as an R package (MicroNiche), represent useful tools to assess microbial environment-taxon and taxon-taxon relationships in a quantitative manner.

Financial impact of sarcopenia on hospitalization costs.

BACKGROUND/OBJECTIVES: This study aims to increase knowledge regarding the association of sarcopenia with hospitalization costs among a wide-ranging sample of adult hospitalized patients. SUBJECTS/METHODS: A prospective study was conducted among hospitalized adult patients. Sarcopenia was identified according to the European Working Group on Sarcopenia in Older People, as low muscle mass, assessed by bioelectrical impedance analysis and low muscle function evaluated by handgrip strength. Hospitalization cost was calculated for each patient based on discharge diagnosis-related group codes and determined on the basis of a relative weight value. Costs were defined as the percentage of deviation from the cost of a patient with a relative weight equal to one. Multivariable linear regression models were performed to identify the factors independently associated with hospitalization costs. RESULTS: A total of 656 hospitalized patients aged ⩾18 years (24.2% sarcopenic) composed the study sample. Sarcopenia increased hospitalization costs by [euro ]1240 (95% confidence interval (CI): [euro ]596-1887) for patients aged <65 years and [euro ]721 (95% CI: [euro ]13-1429) for patients aged ⩾65 years. Sarcopenic overweight was related to an increase in hospitalization costs of [euro ]884 (95% CI: [euro ]295-1476). CONCLUSIONS: Sarcopenia is independently related to hospitalization costs. This condition is estimated to increase hospitalization costs by 58.5% for patients aged <65 years and 34% for patients aged ⩾65 years.

Sarcopenia and length of hospital stay.

BACKGROUND/OBJECTIVES: We aimed to quantify the association of sarcopenia with length of hospital stay (LOS) and to identify factors associated with sarcopenia among hospitalized patients. SUBJECTS/METHODS: A total of 655 patients composed the study sample. A longitudinal study was conducted in a University Hospital. Sarcopenia was defined, according to European Consensus criteria, as low muscle mass (bioelectrical impedance analysis) and low muscle function (handgrip strength). Logistic regression, Kaplan-Meier and Cox adjusted proportional hazards methods were used. LOS was determined from the date of hospital admission and discharge home (event of interest). RESULTS: Participants were aged 18 to 90 years (24.3% sarcopenic). Factors associated with sarcopenia were male gender, age ⩾65 years, moderate or severe dependence, undernutrition and being admitted to a medical ward. Sarcopenic patients presented a lower probability of being discharged home (hazard ratio (HR), 95% confidence interval (CI)=0.71, 0.58-0.86). However, after stratifying for age groups, this effect was visible only in patients aged <65 years (HR, 95% CI= 0.66, 0.51-0.86). Moreover, sarcopenic overweight or obese patients presented a higher probability of being discharged home (HR, 95% CI=0.78, 0.61-0.99) than nonoverweight sarcopenic patients (HR, 95% CI=0.63, 0.48-0.83). CONCLUSIONS: Being male, age ⩾65 years, presenting dependence, being undernourished and admitted to a medical ward were factors associated with sarcopenia among hospitalized adult patients. Sarcopenia is independently associated with longer LOS, although this association is stronger for patients aged <65 years. Moreover, sarcopenic overweight was associated with a higher probability of discharge home than nonoverweight sarcopenia.

Comparative analysis of undernutrition screening and diagnostic tools as predictors of hospitalisation costs.

BACKGROUND: Undernutrition is associated with higher hospitalisation costs. The present study aims (i) to explore whether undernutrition status at hospital admission, as evaluated by different screening and diagnostic tools, can predict patient's hospitalisation costs and (ii) to provide an updated economic analysis of undernutrition burden. METHODS: A prospective study was conducted in a university hospital. Participants' (n = 637) nutritional risk was evaluated within 72 h of admission using the Nutritional Risk Screening (NRS-2002) and the Malnutrition Universal Screening Tool ('MUST'). Undernutrition status was determined by Academy of Nutrition and Dietetics (AND) and American Society for Parenteral and Enteral Nutrition (ASPEN) recommended clinical characteristics and by the Patient Generated Subjective Global Assessment (PG-SGA). The hospitalisation cost was calculated for each inpatient using the diagnosis-related group system. Multivariable linear regression analysis was conducted to identify predictors of hospitalisation costs via percentage deviation from the mean cost, after adjustment for patients' characteristics and comorbidities. RESULTS: Undernutrition risk according to NRS-2002 and high undernutrition risk according to 'MUST' increased patient's costs, respectively, by 21.1% [95% confidence interval (CI) = 9.0-33.2%] and 28.8% (95% CI = 13.7-39.9%). Severe undernutrition by AND-ASPEN recommended clinical characteristics and by PG-SGA was also associated with higher hospitalisation costs, respectively 19.4% (95% CI = 7.3-31.5%) and 27.5% (95% CI = 14.0-41.1%). The cost of a nutritionally-at-risk or undernourished patient is between €416 (95% CI = €156-675) and €617 (95% CI = €293-855) higher than the average of the respective diagnosis-related group. CONCLUSIONS: Undernutrition is a predictor of hospitalisation costs, increasing costs by between 19% and 29%. Undernutrition screening tools have an ability for predicting hospitalisation costs similar to that of diagnostic tools. An updated analysis of undernutrition associated costs was provided, highlighting the economic burden of undernutrition.

Handgrip strength measurement as a predictor of hospitalization costs.

BACKGROUND: Undernutrition status at hospital admission is related to increased hospital costs. Handgrip strength (HGS) is an indicator of undernutrition, but the ability of HGS to predict hospitalization costs has yet to be studied. OBJECTIVE: To explore whether HGS measurement at hospital admission can predict patient's hospitalization costs. SUBJECTS/METHODS: A prospective study was conducted in a university hospital. Inpatient's (n=637) HGS and undernutrition status by Patient-Generated Subjective Global Assessment were ascertained. Multivariable linear regression analysis, computing HGS quartiles by sex (reference: fourth quartile, highest), was conducted in order to identify the independent predictors of hospitalization costs. Costs were evaluated through percentage deviation from the mean cost, after adjustment for patients' characteristics, disease severity and undernutrition status. RESULTS: Being in the first or second HGS quartiles at hospital admission increased patient's hospitalization costs, respectively, by 17.5% (95% confidence interval: 2.7-32.3) and 21.4% (7.5-35.3), which translated into an increase from €375 (58-692) to €458 (161-756). After the additional adjustment for undernutrition status, being in the first or second HGS quartiles had, respectively, an economic impact of 16.6% (1.9-31.2) and 20.0% (6.2-33.8), corresponding to an increase in hospitalization expenditure from €356 (41-668) to €428 (133-724). CONCLUSIONS: Low HGS at hospital admission is associated with increased hospitalization costs of between 16.6 and 20.0% after controlling for possible confounders, including undernutrition status. HGS is an inexpensive, noninvasive and easy-to-use method that has clinical potential to predict hospitalization costs.

Handgrip strength cutoff values for undernutrition screening at hospital admission.

BACKGROUND/OBJECTIVES: There is increasing evidence showing that handgrip strength (HGS) is an indicator of nutrition status and a promising undernutrition screening tool. However, HGS cutoff values for inpatient undernutrition screening remain to be studied. The present study aims to define gender- and age-specific HGS cutoff values for undernutrition screening of hospitalized patients at admission. SUBJECTS/METHODS: A cross-sectional study was conducted in a university hospital. Gender- and age-specific receiver operating characteristic curves were constructed to evaluate the performance of HGS for correctly screening undernourished patients on the basis of their classification by Patient-Generated Subjective Global Assessment. Sensitivity, specificity, areas under the curves (AUCs) and positive likelihood ratios (LRs) were calculated. RESULTS: The study sample was composed of 712 participants between the ages of 18 and 91 years old, median (interquartile range) of 58 (22) years. For women, HGS cutoff values, sensitivities and specificities were as follows: 18-44 years, 20.2 kgf, 0.741 and 0.556; 45-64 years, 19.2 kgf, 0.795 and 0.522. For men, these values were as follows: 18-44 years, 41.7 kgf, 0.923 and 0.520; 45-64 years, 37.9 kgf, 0.817 and 0.402; ⩾65 years, 30.2 kgf, 0.736 and 0.567. The AUCs varied between 0.642 and 0.778 and LRs from 1.37 to 1.92. CONCLUSIONS: This study provides HGS cutoff values for men aged 18-91 years and for women aged 18-64 years.

Hand length as an alternative measurement of height.

BACKGROUND/OBJECTIVES: Despite the utmost importance of body height in evaluating nutritional status, it is not always possible to obtain its measurement and height may have to be estimated. The objective of the study was to formulate and cross-validate a regression equation to predict height using hand length measurement and also to determine if predicted height (PH) will lead to significant errors when used in body mass index (BMI) calculation. SUBJECTS/METHODS: A cross-sectional study was conducted using a consecutive sample of 465 inpatients (19-91 years), from a university hospital. Participants were randomly divided into a development sample of 311 individuals and a cross-validation one. A linear regression model was used to formulate the equation. Intraclass correlation coefficients (ICCs) for single measures and differences between measured height (MH) and PH and between BMI calculated with MH (BMI(MH)) and with PH (BMI(PH)) were determined. RESULTS: The regression equation for PH is: PH (cm)=80.400+5.122 × hand length (cm)--0.195 × age (years)+6.383 × gender (gender: women 0, men 1) (R=0.87, s.e. of the estimate=4.98 cm). MH and PH were strongly correlated, ICCs: 0.67-0.74 (P<0.001). Differences were small, mean difference±s.d., < or = -0.6±4.4 cm (P > or = 0.24). BMI(MH) and BMI(PH) were strongly correlated, ICCs: 0.94-0.96 (P<0.001). Differences were small, < or = 0.3±1.7 kg/m2 (P > or = 0.10). CONCLUSIONS: The formulated regression equation using hand length, age and gender provides a valid estimation of height and is useful in the clinical context. PH from this regression equation can be used in BMI calculations as misclassification is small.

Prevalence of Ca²âº-ATPase-mediated carbonate dissolution among cyanobacterial euendoliths.

Recent physiological work has shown that the filamentous euendolithic cyanobacterium Mastigocoleus testarum (strain BC008) is able to bore into solid carbonates using Ca²âº-ATPases to take up Ca²âº from the medium at the excavation front, promoting dissolution of CaCO3 there. It is not known, however, if this is a widespread mechanism or, rather, a unique capability of this model strain. To test this, we undertook a survey of multispecies euendolithic microbial assemblages infesting natural carbonate substrates in marine coastal waters of the Caribbean, Mediterranean, South Pacific, and Sea of Cortez. Microscopic examination revealed the presence of complex assemblages of euendoliths, encompassing 3 out of the 5 major cyanobacterial orders. 16S rRNA gene clone libraries detected even greater diversity, particularly among the thin-filamentous forms, and allowed us to categorize the endoliths in our samples into 8 distinct phylogenetic clades. Using real-time Ca²âº imaging under a confocal laser scanning microscope, we could show that all communities displayed light-dependent formation of Ca²âº-supersaturated zones in and around boreholes, a staple of actively boring phototrophs. In 3 out of 4 samples, boring activity was sensitive to at least one of two inhibitors of Ca²âº-ATPase transporters (thapsigargin or tert-butylhydroquinone), indicating that the Ca²âº-ATPase mechanism is widespread among cyanobacterial euendoliths but perhaps not universal. Function-community structure correlations point to one particular clade of baeocyte-forming euendoliths as the potential exception.

The biogenicity of modern terrestrial roll-up structures and its significance for ancient life on land.

Roll-up structures (Roll-ups) are sedimentary structures formed by the desiccation-mediated curling of a surface, cohesive layer into a subcylindrical, coiled shape. Their origin in terrestrial environments has been attributed to the shrinking effect of argillaceous components, while microbes are thought to be the curling agent in intertidal marine settings. Roll-ups also exist in terrestrial environments and the rock record, but their genesis is unclear. Proving a biogenic origin of terrestrial roll-ups would make them excellent biosignatures to track ancient life on land. In this study, we tested the biogenicity of modern roll-ups from arid terrestrial environments, showing that, regardless of their geographic location and textural properties, they invariably contained large and distinct cyanobacterial populations compared to adjacent, non-rolled surface soil. Cyanobacterial populations inhabiting these roll-ups were genetically diverse, but consistently dominated by filamentous, non-heterocystous forms. We could also recreate roll-ups artificially by desiccating clay and organic polysaccharide slurries on sandy substrates, and show that clay roll-ups were less prone to re-form after wetting-and-drying cycles and less resistant to erosion than organically bound or naturally occurring ones. All this evidence suggests that fossil roll-ups found in ancient terrestrial deposits are biogenic features.

Effect of biological soil crusts on soil elemental concentrations: implications for biogeochemistry and as traceable biosignatures of ancient life on land.

Biological soil crusts (BSCs) are topsoil biosedimentary structures built by photosynthetic microbes commonly found today on arid soils. They play a role in soil stabilization and the fertility of arid lands, and are considered modern analogues of ancient terrestrial microbial communities. We determined the concentrations of four biogenic and 21 other elements, mostly metals, in surface soils that hosted BSCs, in the soils underneath those crusts, and in proximate but non-crusted surface soils. The samples were from six sites in the Colorado Plateau highlands and the Sonoran Desert lowlands. In spite of the variability in climate and geologic setting, we found statistically significant overall trends of enrichment in biogenic elements and depletion in non-biogenic elements when BSCs were compared with non-crusted soils. The differences between crusted and non-crusted soils were statistically significant at approximately 95% confidence for C, N (enrichments) and for Ca, Cr, Mn, Cu, Zn, As, and Zr (depletions). These trends are best explained by the activity of microbes. As expected, no differences in the concentrations of C, N, P, and S were detected between the soils underneath the crusts and the non-crusted soils, but the former showed depletion of non-biogenic elements, indicating that the leaching effect of crust microbes extends downward in the soil. These patterns speak to the need for a sustained input of allochthonous material, possibly dust, to maintain BSC fertility. These elemental patterns can be considered a biosignature that may be preserved in the rock record and might help identify ancient microbial communities on land.

Molecular genetics and genomic analysis of scytonemin biosynthesis in Nostoc punctiforme ATCC 29133.

The indole-alkaloid scytonemin is the most common and widespread sunscreen among cyanobacteria. Previous research has focused on its nature, distribution, ecology, physiology, and biochemistry, but its molecular genetics have not been explored. In this study, a scytonemin-deficient mutant of the cyanobacterium Nostoc punctiforme ATCC 29133 was obtained by random transposon insertion into open reading frame NpR1273. The absence of scytonemin under conditions of induction by UV irradiation was the single phenotypic difference detected in a comparative analysis of the wild type and the mutant. A cause-effect relationship between the phenotype and the mutation in NpR1273 was demonstrated by constructing a second scytoneminless mutant through directed mutagenesis of that gene. The genomic region flanking the mutation revealed an 18-gene cluster (NpR1276 to NpR1259). Four putative genes in the cluster, NpR1274 to NpR1271, with no previously known functions, are likely to be involved in the assembly of scytonemin. Also in this cluster, there is a redundant set of genes coding for shikimic acid and aromatic amino acid biosynthesis enzymes, leading to the production of tryptophan and tyrosine, which are likely to be biosynthetic precursors of the sunscreen.

Coherence between oxygen saturation and heart rate obtained from pulse oximetric recordings in obstructive sleep apnoea.

In obstructive sleep apnoea (OSA) cyclical changes in oxygen saturation and heart rate in the period range of 30-120 s are observed. In these patients, we prospectively analyse the coherence of nocturnal SaO(2) and heart rate signals. A sample of 201 clinically suspected of having OSA were studied using nocturnal pulse oximetric and complete polysomnography. Coherence function versus period curves were categorized into three patterns: a positive pattern showing a predominant positive peak value of coherence in the period range of 30-120 s; a negative pattern if the predominant coherence was negative in the same range; and an undetermined pattern if no predominance was detected. One hundred and thirteen patients present a positive coherence pattern; 74.3% of these have OSA. A negative coherence pattern was observed for 28 patients; 85.7% of these have OSA. The remaining 60 patients present an undetermined pattern. Patients with OSA presented significantly higher maximal positive coherence and maximal negative coherence than those without OSA. We conclude that OSA patients present dynamic coordination and interdependence between SaO(2) and heart rate in specific frequencies.

Biological soil crusts of sand dunes in Cape Cod National Seashore, Massachusetts, USA.

Biological soil crusts cover hundreds of hectares of sand dunes at the northern tip of Cape Cod National Seashore (Massachusetts, USA). Although the presence of crusts in this habitat has long been recognized, neither the organisms nor their ecological roles have been described. In this study, we report on the microbial community composition of crusts from this region and describe several of their physical and chemical attributes that bear on their environmental role. Microscopic and molecular analyses revealed that eukaryotic green algae belonging to the genera Klebsormidium or Geminella formed the bulk of the material sampled. Phylogenetic reconstruction of partial 16S rDNA sequences obtained from denaturing gradient gel electrophoresis (DGGE) fingerprints also revealed the presence of bacterial populations related to the subclass of the Proteobacteria, the newly described phylum Geothrix/ Holophaga/ Acidobacterium, the Cytophaga/ Flavobacterium/ Bacteroides group, and spirochetes. The presence of these crusts had significant effects on the hydric properties and nutrient status of the natural substrate. Although biological soil crusts are known to occur in dune environments around the world, this study enhances our knowledge of their geographic distribution and suggests a potential ecological role for crust communities in this landscape.

Health-related quality of life in patients with obstructive sleep apnea: effects of long-term positive airway pressure treatment.

The aim of the present study was to determine the effect of middle and long-term positive airway pressure (CPAP) treatment on the health-related quality of life in patients with obstructive sleep apnea. We prospectively studied two groups of patients with this disease; a group of 42 patients (33 men and 9 women) with a mean age of 55.2 +/- 7.4 years and a body mass index of 33.5 +/- 6.4 kg/m2 treated with CPAP for 6-months, and another group of 42 patients (34 men and 8 women) with a mean age of 54.4 +/- 10.5 years and a body mass index of 33.2 +/- 4.0 kg/m2 treated with CPAP for 18-months. The health related quality of life was assessed by administering a Medical Outcomes Study Short Form-36 (SF-36) questionnaire before and after CPAP therapy. Patients treated with CPAP for 6 months only improved significantly in the vitality dimension and this change was clinically relevant (standard error of the measurement = 1.43 SEmeas). In contrast, those treated with CPAP for a long period (18-month) showed statistically significant improvement at post-treatment in five SF-36 dimensions: physical functioning (P < 0.001), role physical (P < 0.01), social functioning (P < 0.01), vitality (P < 0.001), and general health perception (P < 0.001). In four of these dimensions the improvement was clinically relevant: role physical (1.16 SEmeas), social functioning (1.35 SEmeas), vitality (1.35 SEmeas), and general health perception (2.05 SEmeas). Using two different global rating of change (independent measures or anchors), the minimal change important difference for patients treated with CPAP for 6 months ranged from 20.7 to 24.2 points on the vitality dimension; and for patients with CPAP for 18-months it ranged from 2.5 to 7.5 points on the physical role, 5.5-6.6 points on social functioning, 7.5-8.7 on vitality, and 13.5-15.5 on general health perception dimension. We conclude that health-related quality of life of obstructive sleep apnea patients improves with long term CPAP treatment and these changes are clinically relevant in several health dimensions.

Hydrotaxis of cyanobacteria in desert crusts.

We studied the migration of cyanobacteria in desert crusts from Las Bárdenas Reales (Spain). The crusts were almost exclusively colonized by the filamentous cyanobacterium Oscillatoria, which formed a dense layer approximately 600 microm thick located between 1.5 and 2.1 mm deep. Laboratory and field experiments showed that saturation of the crust with liquid water induced a migration of the cyanobacteria leading to a significant greening of the surface within a few minutes. Under light and rapid evaporation, the green color rapidly disappeared and the crust surface was completely devoid of filaments within 60 min. In contrast, 260 min was required to recover the original white color of the crust when slow evaporation was experimentally imposed. The up and down migration following wetting and drying occurred also in the dark. This demonstrates that light was not a required stimulus. Addition of ATP synthesis inhibitors prevented the cyanobacterium from migrating down into the crust, with filaments remaining on the surface. Therefore, the disappearance of the green color observed during desiccation can only be attributed to an active cyanobacterial motility response to the decrease in the water content. The simplest explanation that can account for the evidence gathered is the presence of a mechanism that links, directly or indirectly, these motility responses to gradients in water content, namely a form of hydrotaxis.

Small-scale vertical distribution of bacterial biomass and diversity in biological soil crusts from arid lands in the Colorado plateau.

We characterized, at millimeter resolution, bacterial biomass, diversity, and vertical stratification of biological soil crusts in arid lands from the Colorado Plateau. Microscopic counts, extractable DNA, and plate counts of viable aerobic copiotrophs (VAC) revealed that the top centimeter of crusted soils contained atypically large bacterial populations, tenfold larger than those in uncrusted, deeper soils. The plate counts were not always consistent with more direct estimates of microbial biomass. Bacterial populations peaked at the immediate subsurface (1-2 mm) in light-appearing, young crusts, and at the surface (0-1 mm) in well-developed, dark crusts, which corresponds to the location of cyanobacterial populations. Bacterial abundance decreased with depth below these horizons. Spatially resolved DGGE fingerprints of Bacterial 16S rRNA genes demonstrated the presence of highly diverse natural communities, but we could detect neither trends with depth in bacterial richness or diversity, nor a difference in diversity indices between crust types. Fingerprints, however, revealed the presence of marked stratification in the structure of the microbial communities, probably a result of vertical gradients in physicochemical parameters. Sequencing and phylogenetic analyses indicated that most of the naturally occurring bacteria are novel types, with low sequence similarity (83-93%) to those available in public databases. DGGE analyses of the VAC populations indicated communities of lower diversity, with most types having sequences more than 94% similar to those in public databases. Our study indicates that soil crusts represent small-scale mantles of fertility in arid ecosystems, harboring vertically structured, little-known bacterial populations that are not well represented by standard cultivation methods.

Cyanobacterial diversity in extreme environments in Baja California, Mexico: a polyphasic study

Cyanobacterial diversity from two geographical areas of Baja California Sur, Mexico, were studied: Bahia Concepcion, and Ensenada de Aripez. The sites included hypersaline ecosystems, sea bottom, hydrothermal springs, and a shrimp farm. In this report we describe four new morphotypes, two are marine epilithic from Bahia Concepcion, Dermocarpa sp. and Hyella sp. The third, Geitlerinema sp., occurs in thermal springs and in shrimp ponds, and the fourth, Tychonema sp., is from a shrimp pond. The partial sequences of the 16S rRNA genes and the phylogenetic relationship of four cyanobacterial strains (Synechococcus cf. elongatus, Leptolyngbya cf. thermalis, Leptolyngbya sp., and Geitlerinema sp.) are also presented. Polyphasic studies that include the combination of light microscopy, cultures and the comparative analysis of 16S rRNA gene sequences provide the most powerful approach currently available to establish the diversity of these oxygenic photosynthetic microorganisms in culture and in nature (AU)

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